科普 神奇的宇宙----图片(每天更新中)

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Ring Galaxy AM 0644-741 from Hubble

Explanation: How could a galaxy become shaped like a ring? The rim of the blue galaxy pictured on the right is an immense ring-like structure 150,000 light years in diameter composed of newly formed, extremely bright, massive stars. That galaxy, AM 0644-741, is known as a ring galaxy and was caused by an immense galaxy collision. When galaxies collide, they pass through each other -- their individual stars rarely come into contact. The ring-like shape is the result of the gravitational disruption caused by an entire small intruder galaxy passing through a large one. When this happens, interstellar gas and dust become condensed, causing a wave of star formation to move out from the impact point like a ripple across the surface of a pond. The intruder galaxy has since moved out of the frame taken by the Hubble Space Telescope and released to commemorate the anniversary of Hubble's launch in 1990. Ring galaxy AM 0644-741 lies about 300 million light years away.

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Molecular Cloud Barnard 68

Credit: FORS Team, 8.2-meter VLT Antu, ESO
Explanation: Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. It is possible to look right through the cloud in infrared light.

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Cat's Eye Hubble Remix

Credit & Copyright: Vicent Peris (OAUV / PTeam), MAST, STScI, AURA, NASA
Explanation: Staring across interstellar space, the alluring Cat's Eye Nebula lies three thousand light-years from Earth. One of the most famous planetary nebulae in the sky, the Cat's Eye (NGC 6543) is over half a light-year across and represents a final, brief yet glorious phase in the life of a sun-like star. This nebula's dying central star may have produced the simple, outer pattern of dusty concentric shells by shrugging off outer layers in a series of regular convulsions. But the formation of the beautiful, more complex inner structures is not well understood. Here, Hubble Space Telescope archival image data has been reprocessed to create another look the cosmic cat's eye. Compared to well-known Hubble pictures, the alternative processing strives to sharpen and improve the visiblility of details in light and dark areas of the nebula and also applies a more complex color palette. Of course, gazing into the Cat's Eye, astronomers may well be seeing the fate of our Sun, destined to enter its own planetary nebula phase of evolution ... in about 5 billion years.

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Where is HD 189733?

Image Credit: NASA, ESA, A. Fujii, and Z. Levay (STScI)
Explanation: The star cataloged as HD 189733 is a mere 63 light-years away. Its location is indicated in this deep, wide-angle image of the sky centered on the northern constellation of Cygnus. Considering the many bright stars, nebulae, and star clusters in the region more familiar to skygazers, HD 189733 may not seem to be remarkable, but it is known to have at least one hot, jupiter-sized planet orbiting very close, with an impressively short period of 2.2 days. Because the planet regularly eclipses its parent star, astronomers can study starlight that passes directly through the planet's atmosphere and identify molecules through spectroscopy. Following the discovery of water vapor in the planetary atmosphere, astronomers now report that Hubble Space Telescope data also indicates the signature of methane (CH4). The exciting result is the first detection of an organic molecule on a planet orbiting another star. Although HD 189733's planet is considered too hot and inhospitable to support life, the work is a step toward measuring conditions and chemistry on other extrasolar planets where life could exist.

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AE Aurigae: The Flaming Star

Explanation: Is star AE Aurigae on fire? No. Even though AE Aurigae is named the flaming star, the surrounding nebula IC 405 is named the Flaming Star Nebula, and the region appears to harbor red smoke, there is no fire. Fire, typically defined as the rapid molecular acquisition of oxygen, happens only when sufficient oxygen is present and is not important in such high-energy, low-oxygen environments such as stars. The material that appears as smoke is mostly interstellar hydrogen, but does contain smoke-like dark filaments of carbon-rich dust grains. The bright star AE Aurigae, visible just below the image center, is so hot it is blue, emitting light so energetic it knocks electrons away from surrounding gas. When a proton recaptures an electron, red light is frequently emitted, as seen in the surrounding emission nebula. Pictured above, the Flaming Star nebula lies about 1,500 light years distant, spans about 5 light years, and is visible with a small telescope toward the constellation of the Charioteer (Auriga).

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Short Gamma-Ray Bursts Localized

Explanation: What causes gamma-ray bursts? The most energetic type of explosions known in the cosmos has been an enigma since discovered over 30 years ago. It now appears that there may not be one unique type of progenitor. Long duration gamma-ray bursts (GRBs) have been localized, over the past few years, to blue regions in the universe rich in star formation. Massive young stars nearing the end of their short lives commonly explode in these regions. Astronomers associate these long duration GRBs, that can last from seconds to minutes, with a type of stellar explosion common in young massive stars. Over the past few months, short duration GRBs have finally been localized and found to occur in different types of regions -- not only blue regions rich in star formation. Many astronomers therefore now theorize that short GRBs, which typically last less than one second, are the result of a different progenitor process than long GRBs. A leading model is that a short GRB will occur when a neutron star either impacts another neutron star or a black hole. Such collisions may occur well after star-forming regions have otherwise burned out. Pictured in the above illustration, two energized neutrons stars finally approach each other in their orbits, a death spiral that might end with a short GRB.

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Astronomy Quilt of the Week

Explanation: Demonstrating her mastery of a traditional astronomical imaging technique quilter and astronomy enthusiast Judy Ross has produced this spectacular composition of "Astronomy Quilt Piece of the Week". Her year-long effort resulted in an arrangement for a six by seven foot quilt consisting of 52 individual pieces (11 inches by 8 inches), one for each week, which she reports were inspired by her steady diet of APOD's daily offerings. Some of the pieces are based on actual pictures, such as the Hubble Space Telescope's view of planet forming AB Aurigae or Bill Keel's image of the nearby Pinwheel Galaxy. Others, with titles like the Blue Carpet Nebula and Duck Contemplates Black Hole, are from her own creative imaginings.

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Dusty Environs of Eta Carinae

Explanation: Eta Car is a massive star, but it's not as bright as it used to be. Now only easily visible in binoculars or a small telescope, Eta Carinae has a history of spectacular flaring and fading behavior. In fact, in April of 1843 Eta Car briefly became second only to Sirius as the brightest star in planet Earth's night sky, even though at a distance of about 7,500 light-years, it is about 800 times farther away. Surrounded by a complex and evolving nebula, Eta Carinae is seen near the center of this false-color infrared image, constructed using data from the Midcourse Space Experiment (MSX). The MSX satellite mapped the galactic plane in 1996. In the picture, wispy, convoluted filaments are clouds of dust glowing at infrared wavelengths. Astronomers hypothesize that Eta Car itself will explode as a supernova in the next million years or so. Massive Eta Car has even been considered a candidate for a hypernova explosion and the potential source of a future gamma-ray burst.

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Alnitak, Alnilam, Mintaka

Explanation: Alnitak, Alnilam, and Mintaka, are the bright bluish stars from east to west (left to right) along the diagonal in this gorgeous cosmic vista. Otherwise known as the Belt of Orion, these three blue supergiant stars are hotter and much more massive than the Sun. They lie about 1,500 light-years away, born of Orion's well-studied interstellar clouds. In fact, clouds of gas and dust adrift in this region have intriguing and some surprisingly familiar shapes, including the dark Horsehead Nebula and Flame Nebula near Alnitak at the lower left. The famous Orion Nebula itself lies off the bottom of this star field that covers an impressive 4.4x3.5 degrees on the sky. The color picture was composited from digitized black and white photographic plates recorded through red and blue astronomical filters, with a computer synthesized green channel. The plates were taken using the Samuel Oschin Telescope, a wide-field survey instrument at Palomar Observatory, between 1987 and 1991.

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NGC 869 & NGC 884: A Double Open Cluster

Explanation: Most star clusters are singularly impressive. Open clusters NGC 869 and NGC 884, however, are doubly impressive. Also known as "h and chi Persei", this unusual double cluster, shown above, is bright enough to be seen from a dark location without even binoculars. Although their discovery surely predates written history, the Greek astronomer Hipparchus notably cataloged the "double cluster". The clusters are over 7,000 light years distant toward the constellation of Perseus, but are separated by only hundreds of light years.

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Peculiar Arp 295

Explanation: A spectacular bridge of stars and gas stretches for nearly 250,000 light-years and joins this famous peculiar pair of galaxies cataloged as Arp 295. The cosmic bridge between the galaxies and the long tail extending below and right of picture center are strong evidence that these two immense star systems have passed close to each other in the past, allowing violent tides induced by mutual gravity to create the eye-catching plumes of stellar material. While such interactions are drawn out over billions of years, repeated close passages should ultimately result in the merger of this pair of galaxies into a larger single galaxy of stars. Although this scenario does look peculiar, galactic mergers are thought to be common, with Arp 295 representing an early stage of this inevitable process. The Arp 295 pair are the largest of a loose grouping of galaxies about 270 million light-years distant toward the constellation Aquarius. This deep color image of the region was recorded in September 2003 using the USNO 1 meter telescope near Flagstaff, Arizona.

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Eclipse Madrid

Explanation: A walk in the park seemed like a perfect idea to many enjoying a sunny October morning in Madrid, Spain. Of course, on October 3rd an added attraction was the Moon - seen in dramatic silhouette during an annular solar eclipse. This multiple exposure sequence follows the progress of the eclipse from Madrid's monument to King Alfonso XII in the pleasant Parque del Buen Retiro. The Sun rises at the left and moves up and to the right in the picture, with the ring-like annular phase near picture center. While a partial eclipse was visible over a wide area including Europe, Africa and western Asia, the central line of the shadow track crossed Madrid. Sun watchers in the capital city basked in an annular eclipse phase lasting about four minutes.

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Spiral Galaxy NGC 1350

Explanation: This gorgeous island universe lies about 85 million light-years distant in the southern constellation Fornax. Inhabited by young blue star clusters, the spiral arms of NGC 1350 seem to join in a circle around the galaxy's large, bright nucleus - giving the galaxy the appearance of a limpid cosmic eye. NGC 1350 is about 130,000 light-years across making it as large or slightly larger than our own Milky Way. For earth-based astronomers, NGC 1350 is seen on the outskirts of the Fornax cluster of galaxies, but its estimated distance suggests that it is not itself a cluster member. The sharp image also reveals many background galaxies, some visible right through NGC 1350.

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Annular Solar Eclipse at High Resolution

Explanation: On Monday, part of the Sun went missing. The missing piece was no cause for concern -- the Moon was only momentarily in the way. The event was not a total eclipse of the Sun for any Earth-bound sky enthusiast but rather, at best, an annular eclipse, where the Moon blocked most of the Sun. Because of the relatively large distance to the Moon during this Earth-Moon-Sun alignment, the Moon did not have a large enough angular size to block the entire Sun. Those who witnessed the solar eclipse from a narrow path through Portugal, Spain and Africa, however, were lucky enough to see the coveted Ring of Fire, a dark Moon completely surrounded by the brilliant light of the distant Sun. Pictured above is a Ring of Fire captured two days ago in unusually high resolution above Spain. The resulting image shows details of the granular solar surface as well as many prominences around the Sun.

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Magma Bubbles from Mt. Etna

Explanation: Mt. Etna erupted spectacularly in 2001 June. Pictured above, the volcano was photographed expelling bubbles of hot magma, some of which measured over one meter across. One reason planetary geologists study Earth's Mt. Etna is because of its likely similarity to volcanoes on Mars. Mt. Etna, a basalt volcano, is composed of material similar to Mars, and produces similar lava channels. Located in Sicily, Italy, Mt. Etna is not only one of the most active volcanoes on Earth, it is one of the largest, measuring over 50 kilometers at its base and rising nearly 3 kilometers high.

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NGC 613: Spiral of Dust and Stars

Explanation: When morning twilight came to the Paranal Observatory in Chile, astronomers Mark Neeser and Peter Barthel interrupted their search for faint quasars, billions of light-years away. And just for a moment, they used Very Large Telescopes at the European Southern Observatory to appreciate the beauty of the nearby Universe. One result was this stunning view of beautiful barred spiral galaxy NGC 613, a mere 65 million light-years away in the southern constellation Sculptor. Over 100 thousand light-years across, NGC 613 seems to have more than its fair share of spiral arms laced with cosmic dust clouds and bright star forming regions near the ends of a dominant central bar. Radio emission indicates the presence of a massive black hole at the center of NGC 613.

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An Unexplored Nebula

Explanation: The combined light of the stars of the Milky Way are reflected by this cosmic dust cloud that soars some 300 light-years above the plane of our Galaxy. Dubbed the Angel Nebula by astronomer Steve Mandel's 13 year old son, the dusty apparition is part of an expansive complex of dim and relatively unexplored diffuse nebulae, traced over large regions seen toward the North and South Galactic poles. Along with the blue tint characteristic of more commonly observed reflection nebulae, the Angel Nebula and other dusty galactic cirrus also produce a faint reddish luminescence, as dust grains convert the Milky Way's invisible ultraviolet radiation to visible red light. Spanning 3x4 degrees on the sky in the constellation Ursa Major, this wide-angle, high-resolution image was recorded as part of the Unexplored Nebula Project.

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The Star Pillars of Sharpless 171

Explanation: Towering pillars of cold gas and dark dust adorn the center star forming region of Sharpless 171. An open cluster of stars is forming there from the gas in cold molecular clouds. As energetic light emitted by young massive stars boils away the opaque dust, the region fragments and picturesque pillars of the remnant gas and dust form and slowly evaporate. The energetic light also illuminates the surrounding hydrogen gas, energize it to glow as a red emission nebula. Pictured above is the active central region of the Sharpless 171 greater emission nebula. Sharpless 171 incorporates NGC 7822 and the active region Cederblad 214, much of which is imaged above. The area above spans about 20 light years, lies about 3,000 light years away, and can be seen with a telescope toward the northern constellation of the King of Ethiopia (Cepheus).

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Streams of Stars in the Virgo Cluster of Galaxies

Explanation: How do huge clusters of galaxies evolve? To help find out, astronomers pointed the wide-angle Burrell-Schmidt telescope on Kitt Peak National Observatory in Arizona, USA at the nearby Virgo Cluster of Galaxies. After hundreds of 15-minute exposures taken over two months in early 2004, the result is a dramatically deep and wide angle image of Virgo, the closest cluster of galaxies to our Milky Way Galaxy. Bright foreground stars have been digitally removed from the image but are still represented by numerous unusual dark spots. Inspection of the above image shows unusually large halos for the brightest galaxies as well as unusual faint streams of stars connecting Virgo galaxies that previously appeared unrelated. The above image allows a better reconstruction of the past few billion years of the gigantic Virgo cluster and illuminates the dynamics of clusters of galaxies in general.

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WMAP Resolves the Universe

Explanation: Analyses of a new high-resolution map of microwave light emitted only 380,000 years after the Big Bang appear to define our universe more precisely than ever before. The eagerly awaited results announced last year from the orbiting Wilkinson Microwave Anisotropy Probe resolve several long-standing disagreements in cosmology rooted in less precise data. Specifically, present analyses of above WMAP all-sky image indicate that the universe is 13.7 billion years old (accurate to 1 percent), composed of 73 percent dark energy, 23 percent cold dark matter, and only 4 percent atoms, is currently expanding at the rate of 71 km/sec/Mpc (accurate to 5 percent), underwent episodes of rapid expansion called inflation, and will expand forever. Astronomers will likely research the foundations and implications of these results for years to come.